How does the relative humidity of the atmosphere affect the photosynthetic rate of plants?

Relative humidity affects the photosynthetic rate of plants by influencing the rate of transpiration and gas exchange. High humidity can reduce transpiration, leading to less water uptake and potentially limiting nutrient transport, while low humidity increases transpiration, which can enhance gas exchange but also risk water loss. Optimal humidity levels encourage efficient stomatal opening, facilitating carbon dioxide absorption for photosynthesis. Thus, both extremes can negatively impact plant health and productivity.